Tricuspid valve malformation is a rare congenital heart disease. Prenatal diagnosis of Ebstein's anomaly (EA) and tricuspid valve dysplasia (TVD) is associated with high mortality. There are conflicting reports concerning accurate prognostication after diagnosis in utero. The aim of our study was to assess prognostic factors based on our experience. We reviewed 37 fetuses between 1984 and June 2010 comprising 26 cases of EA and 11 cases of TVD. There were 10 terminations, 5 intrauterine deaths, 8 neonatal deaths, and 14 survivors. We found that the major prognostic factor for outcome was the flow pattern through the pulmonary valve on the first echocardiogram. Retrograde flow was strongly correlated with fetal or neonatal death (p = 8 × 10(-5)), and anterograde flow predicted good outcome (p = 8 × 10(-5)). In contrast, cardiothoracic indexes, right to left-ventricular ratio, and Celermajer index were not useful prognostic markers. The Simpson Andrews Sharland score, which was more complex, was well correlated with our series. Flow through the pulmonary valve on the first echocardiogram is a simple and excellent prognostic factor when major tricuspid valve disease is diagnosed in utero. Fetuses should be monitored throughout pregnancy, particularly those with retrograde ductus arteriosus, because several hemodynamic factors may worsen the prognosis.